Dark data is the information your company collects but doesn’t use—often 55% of...

https://blogfreely.net/samuel-wang09/how-do-i-check-if-dark-data-contains-pii-or-phi

Dark data is the information your company collects but doesn’t use—often 55% of stored files. It increases storage and backup costs and raises breach risk, including ransomware attacks, since unused data is less monitored